Force collections to be static (#68723)

* Force collections to be static

Templating of collection names does not work at all. Force them to
be static so that a warning is generated for the user.

* Add collectionsearch unit test and fix for reviews

New unit test validates the new _load_collections() code and moves
the new check to the end of the method.

* Change unit test to pytest

* Adjust unit test to use capsys instead of monkeypatch

* Fix pep8 error

* Add changelog fragment

Closes #68704

changelogs/fragments/68723-force-static-collections.yaml

@@ -0,0 +1,3 @@
+bugfixes:
+- Force collection names to be static so that a warning is generated because
+  templating currently does not work (see https://github.com/ansible/ansible/issues/68704).

lib/ansible/playbook/collectionsearch.py

@@ -7,6 +7,10 @@ __metaclass__ = type
 from ansible.module_utils.six import string_types
 from ansible.playbook.attribute import FieldAttribute
 from ansible.utils.collection_loader import AnsibleCollectionLoader
+from ansible.template import is_template, Environment
+from ansible.utils.display import Display
+
+display = Display()
 
 
 def _ensure_default_collection(collection_list=None):
@@ -32,7 +36,8 @@ def _ensure_default_collection(collection_list=None):
 class CollectionSearch:
 
     # this needs to be populated before we can resolve tasks/roles/etc
-    _collections = FieldAttribute(isa='list', listof=string_types, priority=100, default=_ensure_default_collection)
+    _collections = FieldAttribute(isa='list', listof=string_types, priority=100, default=_ensure_default_collection,
+                                  always_post_validate=True, static=True)
 
     def _load_collections(self, attr, ds):
         # this will only be called if someone specified a value; call the shared value
@@ -41,4 +46,13 @@ class CollectionSearch:
         if not ds:  # don't return an empty collection list, just return None
             return None
 
+        # This duplicates static attr checking logic from post_validate()
+        # because if the user attempts to template a collection name, it will
+        # error before it ever gets to the post_validate() warning.
+        env = Environment()
+        for collection_name in ds:
+            if is_template(collection_name, env):
+                display.warning('"collections" is not templatable, but we found: %s, '
+                                'it will not be templated and will be used "as is".' % (collection_name))
+
         return ds

test/units/playbook/test_collectionsearch.py

@@ -0,0 +1,38 @@
+# (c) 2020 Ansible Project
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from ansible.playbook.collectionsearch import CollectionSearch
+
+import pytest
+
+
+def test_collection_static_warning(capsys):
+    """Test that collection name is not templated.
+
+    Also, make sure that users see the warning message for the referenced name.
+    """
+
+    collection_name = 'foo.{{bar}}'
+    cs = CollectionSearch()
+    assert collection_name in cs._load_collections(None, [collection_name])
+
+    std_out, std_err = capsys.readouterr()
+    assert '[WARNING]: "collections" is not templatable, but we found: %s' % collection_name in std_err
+    assert '' == std_out